Free-Living Protozoa

Instructions This key will aid students in the identification of protozoa normally encountered in our cultures. Line drawings of each protozoan, along with designations of size range, are included inside this sheet. It is suggested that DETAIN, WARD'S protozoan slowing agent, be used to slow the faster-moving protozoa. A wet mount preparation should first be scanned under low power magnification to initially locate protozoa for observation and identification. In some cases, identification will be made easier if cells are examined under "high-dry" magnification (450X).

Identification of a protozoan may be made by either comparing the observed cell to the illustrations on this sheet or by using the key. The key gives the student two choices per number. Start at number 1, comparing the observed protozoan to each of the characteristics stated per number in the key. Proceed according to the key until it terminates in the name of the protozoan.

1. White or colorless ...... 2 Colored ...... 8 2. Creeping (sliding) slowly or floating without apparent motion ...... 3 Exhibits other motion ...... 7 3. Spherically shaped with radiating "spines" ...... Actinosphaerium Not spherical in shape ...... 4 4. Shape remains constant ...... 5 Shape constantly changes ...... 6 5. Possesses flattened test or shell without embedded or attached material; pale to brown in color ...... Arcella Possesses dome-shaped test or shell with attached particles,usually of sand ...... Difflugia 6. Small; creeps using pseudopodia (false feet); single disc-shaped nucleus ...... Amoeba Large; creeps using pseudopodia; many (1OO's) of small nuclei ...... Pelomyxa 7. Cell has hair-like structures (cilia) ...... 16 Cell's organ of locomotion is long whip-like flagella (no cilia) ...... 9 8. Green color ...... 9 Color not green ...... 23 9. Colony of many cells ...... 11 Single, motile cells ...... 10 10. One observed locomotor flagella ...... 15 Two observed locomotor flagella ...... 14 11. Colony flat, disc-shaped, usually containing sixteen cells ...... Gonium Colony spherical in shape ...... 12 12. Colony contains 32 cells or less...... 13 Colony contains more than 32 cells ...... Volvox

Side View

Gonium Pelomyxa Colony up to 90 µm 1-5 mm, Arcella in diameter monopodal length 45 - 100 µm in diameter Spirostomum 1-3 mm in length

Actinosphaerium Eudorina Chilomonas sp. Pandorina 70 - 80 µm in diameter 10-24 µm in diameter 20-40 µm colony from 20-250 µm in diameter

Amoeba proteus Chlamydomonas Colpidium sp. Difflugia up to 600 µm or more, 5-12 µm in length 50-70 µm inlength 60-580 µm by elongated 40-240 µm

illustrations not to scale

US: P.O. Box 92912 • Rochester, NY • 14692-9012 | 812A Fiero Lane • San Luis Obispo, CA 93401 • 800-962-2660 Canada: 399 Vansickle Road • St. Catharines, ON L2S 3T4 • 800-387-7822 www.wardsci.com Euplotes sp. Euglena Peranema sp. Volvox 100 - 200 µm in length 35 - 55 µm 20 - 70 µm in length colony from in length 350 - 500 µm in diameter

Stentor coeruleus Bursaria truncatella Didinium Didinium Cyst 1 - 2 mm, extended 500 - 1,000 µm in length 80 - 200 µm in length

Paramecium Species

Paramecium Paramecium aurelia bursaria 70 - 110 µm in length 120 - 180 µm in length

Vorticella Blepharisma sp. Paramecium Paramecium 5 - 15 µm in length 400 - 600 µm in length multimicronucleatum caudatum 200 - 300 µm in length 180 - 300 µm in length

13. Colony contains 32 cells ...... Eudorina Colony contains sixteen cells ...... Pandorina 14. Cell elongated with narrowed posterior ...... Chilomonas Cell oval-shaped ...... Chlamydomonas 15. Cell elongated, green in color ...... Euglena Cell elongated, colorless, with a broad, rounded or truncate posterior during locomotion; highly plastic when stationary, often appears to vibrate when in motion ...... Peranema 16. Body has specialized groups of cilia, or cilia in specific areas ...... 17 Body entirely covered with cilia ...... 19 17. Cell not on stalk ...... 18 Cell on stalk; cells contract (stalk appears to contract like a spring) ...... Vorticella 18. Cell oval-shaped with distinct point-like projections termed cirri (fused cilia); travels by "walking" using cirri ...... Euplotes Cell oval-shaped with two distinct ciliary bands, one anterior and one in the middle of the body; swims with spiral motion ...... Didinium 19. Body trumpet-shaped or elongated ...... 20 Body oval-shaped ...... 22 20. Body elongated; never attached to substrate ...... 21 Body trumpet-shaped; usually attached to substrate ...... Stentor 21. Large cell with elongated, flattened body with blunt ends; contracts to 1/4 of its body length when stimulated ...... Spirostomum Small cell with elongated body, "cigar-shaped," with rounded ends; swims rapidly in a corkscrew fashion ...... Paramecium* 22. Small body, oval shaped, with small mouth; fast swimmer ...... Colpidium Extremely large body (visible with the naked eye), with large, wide mouth ...... Bursaria truncatella 23. Pink or rose-colored (ciliate) ...... Blepharisma Dark bluish-green (ciliate) ...... Stentor *many species, see diagram